Method and apparatus for vertical S linearity correction with no external components

• US 6,577,083 B1
• Filed: 10/09/2001
• Issued: 06/10/2003
• Est. Priority Date: 10/09/2001
• Status: Active Grant

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Guan, Charles Yong Yi
• Primary Examiner(s): Oda, Christine
• Assistant Examiner(s): Lair, Donald M
• Application Number:
  US09/973,789
• Time in Patent Office: 609 Days
• Field of Search: 324/88, 324/436, 315/365, 315/368.18, 315/370, 315/387, 315/364
• US Class Current: 315/370
• CPC Class Codes: G09G 1/04 Deflection circuits ; Constructional details not otherwise provided for electron-optical arrangements H01J29/46, H01J37/04, H01J37/302
• CPC Class Codes: H04N 3/2335 with calculating means

Abstract

A method and apparatus for vertical S linearity correction with no external components. A periodic waveform may be cubed to produce a second waveform. This second waveform may be sampled to obtain a peak value of the periodic waveform. The peak value may be multiplied by a constant to produce an offset value. The offset value may be subtracted from the second waveform to produce a third waveform. This third waveform may be added to the periodic ramp voltage. Consequently, the periodic waveform is modified by a cubic waveform.

Claims

1. A method of processing a periodic waveform comprising:

cubing said periodic waveform to produce a second waveform;

sampling a peak value of said second waveform;

multiplying said peak value by a constant to produce an offset value;

subtracting said offset value from said second waveform to produce a third waveform; and

adding said third waveform to said periodic waveform.

2. The method of claim 1 wherein said periodic waveform is a ramp voltage for controlling vertical deflection in a cathode ray tube.

3. The method of claim 1 wherein said constant is 0.25.

4. The method of claim 1 wherein said processing produces a ramp voltage with s linearity correction for controlling vertical deflection in a cathode ray tube.

5. An electronic circuit for determining the average value of an applied current waveform comprising:

an input for accessing said current waveform;

a sample and hold circuit coupled to said input for determining the peak value of said current waveform;

a current scaling circuit coupled to said sample and hold

circuit for scaling the peak value of said current waveform;

an output coupled to said current scaling circuit,

wherein said output is the average value of a current applied to said input; and

wherein said output is one quarter of the peak current of a current applied to said input.

6. An electronic circuit for determining the average value of an applied current waveform comprising:

an input for accessing said current waveform;

a sample and hold circuit coupled to said input for determining the peak value of said current waveform;

a current scaling circuit coupled to said sample and hold circuit for scaling the peak value of said current waveform;

an output coupled to said current scaling circuit,

wherein said output is the average value of a current applied to said input; and

wherein a current applied to said input is the cube of a periodic ramp voltage, wherein said periodic ramp voltage is generated to control the vertical deflection in a cathode ray tube.

7. An electronic circuit for determining the average value of an applied current waveform comprising:

an input for accessing said current waveform;

a sample and hold circuit coupled to said input for determining the peak value of said current waveform;

a current scaling circuit coupled to said sample and hold circuit for scaling the peak value of said current waveform;

an output coupled to said current scaling circuit,

wherein said output is the average value of a current applied to said input;

a first adder coupled to said output for adding two current waveforms;

a current to voltage converter coupled to said first adder for converting a current waveform to a voltage waveform; and

a second adder coupled to said current to voltage converter for adding two voltage waveforms;

wherein said output is added to said input in said first adder, producing an AC current waveform, which is converted to a voltage waveform by said current to voltage converter; and

wherein said voltage waveform is added to a vertical deflection voltage by said second adder, producing an s linearity corrected ramp voltage to control the vertical deflection of a cathode ray tube.

8. The electronic circuit of claim 7 realized on an integrated circuit.